1. Technical Field
The invention generally relates to the field of display technology, and particularly to an optical alignment device and a spatial beam splitting prism thereof.
2. Description of Related Art
Thin film transistor liquid crystal display (TFT-LCD) devices in recent years have had rapid development and wide applications. In brief, The TFT-LCD device can be regarded as two glass substrates with a layer of liquid crystal interposed therebetween, the upper glass substrate being a color filter, and the lower glass substrate being disposed with thin film transistors. When a current flows through the thin film transistor, a change of electric field is generated, and the change of electric field causes liquid crystal molecules to be deflected, which would change the polarity of light and thereby achieve a desired display purpose. Before applying a voltage, the liquid crystal molecules are necessarily made to have an initial orientation/alignment direction, and therefore alignment films usually are needed in the display panel and for controlling arrangement direction and angle of the liquid crystal molecules.
With the progress of alignment technology, an alignment process of optical alignment technology has gradually replaced the traditional rubbing alignment process. The role of an optical alignment film is to replace traditional raised structures or trench structures, which avoids the light leakage caused by the traditional raised and trench structures, greatly improves the aperture ratio, and makes liquid crystal molecules of sub-pixel area to have an initial pre-tilt angle so that the response speed is increased.
As illustrated in FIG. 1, in the current optical alignment technology, usually, a glass substrate 200 firstly is coated with an alignment film 300, a polarized UV light then is used to irradiate the alignment film 300 at a certain angle of inclination (i.e., exposure) so as to perform an alignment processing on the alignment film 300. By such processing, when liquid crystal molecules 500 are filled between glass substrates, the liquid crystal molecules 500 would have a pre-tilt angle along a certain direction.
FIG. 2A through FIG. 2E illustrate a process of performing multi-area alignments by current optical alignment technology. As illustrated in FIG. 2A, a planar photomask 100 with a plurality of opaque blocking strips 101 spaced from each other is disposed on a glass substrate 200 coated with an optical alignment film, an obliquely incident polarized UV light then is used to irradiate the alignment film so as to perform a first time UV alignment. As illustrated in FIG. 2B, the areas 301 are areas performed with the first time alignment, and the arrows A represent the first time alignment direction. Subsequently, as illustrated in FIG. 2C, the glass substrate 200 performed with the first time alignment is rotated with 180 degrees. Then, as illustrated in FIG. 2D, the blocking strips 101 of the planar photomask 100 are used to align with and cover the areas 301 performed with the first time UV alignment, so as to achieve the alignment of the planar photomask 100. After that, the obliquely incident polarized UV light is used to irradiate again, so as to complete a second time UV alignment, the areas 302 are areas completed with the second time alignment, and the arrows B represent the second time alignment direction (as denoted in FIG. 2E). Therefore, in the above mentioned optical alignment process, if it is required to perform alignments to different areas, it must to rotate the glass substrate 200 several times to perform multiple exposures or change the incident direction of the UV light multi-times, so as to achieve the purpose of multi-area alignments. Such multiple UV irradiations not only cause long working hours for a single piece, but also during the process of performing the multiple UV irradiations corresponding to the multi-times rotations of the glass substrate, the alignment error of the planar photomask would cause the decrease of precision and meanwhile cause a higher risk of workpiece being broken.